p38 Mitogen-Activated Protein Kinase (MAPK) and Steroid Insensitivity in Asthma

p38 MAPK Activation as the Basis for Corticosteroid Insensitivity in Severe Asthma

This research aims to find out how the inflammation in patients suffering from severe asthma is different from that in non-severe asthma, and how it may prevent corticosteroids from working efficiently in severe asthma.

It will look,in particular, at a protein enzyme called p38 mitogen-activated protein kinase (p38 MAPK for short)which controls the activation of several important pathways in the cell. We wish to find out whether this enzyme is more active in cells obtained from patients with severe asthma compared to those with non-severe asthma. We would like to understand how this enzyme can cause the cell to respond less well to the anti-inflammatory effects of corticosteroids. We also wish to find out whether any specific inhibitors of p38 MAPK can improve severe asthma by improving the effects of corticosteroids on these cells.

We hypothesise that activation of the intracellular MAPK signalling pathway underlies the inflammatory processes of severe asthma, and leads to the diminution of the anti-inflammatory actions of CS through histone modification.

DESIGN Comparative study to analyse differences in the characteristics of lung macrophages and blood monocytes between non-severe and severe asthmatics.

AIMS

1. To determine whether there are differences in terms of cell expression and activation between lung macrophages and blood monocytes from non-severe and severe asthma
2. To determine the mechanisms of the lung macrophage and blood monocyte relative resistance to the effect of corticosteroids in severe asthma, and particularly focus on the role of p38 MAPK
3. To determine the differences in airway smooth muscle cells between non-severe and severe asthma

OUTCOME MEASURES

1. Clinically the differences in inflammatory and remodelling markers between non-severe and severe asthma
2. Differences in histone phosphorylation, NF-kB activity and glucocorticoid receptor activation and actions in macrophages and monocytes between non- severe and severe asthma
3. Differences in behaviour of airway smooth muscle cells cultured from biopsies obtained from non-severe and severe asthma

Severe and non-severe asthmatic subjects will be classified following ATS criteria. They undergo spirometry with reversibility testing, PC20, skin prick tests, exhaled nitric oxide measurements and induced sputum. They will have blood taken for PBMCs and undergo fiberoptic bronchoscopy for obtention of alveolar macrophages and bronchial biopsies

Inclusion Criteria:

• Age 18-60
• Physician diagnosis of asthma

Non-severe asthmatic subjects:

• mild to moderately severe asthma.

• The groups will be defined as follows, according to their need for treatments (as established in the Asthma Management GINA or BTS guidelines):

  1. Mild: intermittent symptoms and need for reliever bronchodilator less than once a day
  2. moderate asthma: well-controlled asthma with minimal symptoms while on inhaled corticosteroid therapy not exceeding 2,000 μg beclomethasone equivalent.

Severe asthmatic subjects:

• will have at least 1 major and 2 minor criteria (as below) Major characteristics (at least one of the following criteria)

  • Treatment with continuous or near continuous (>50% of year) oral corticosteroids

  • Requirement for treatment with high dose inhaled corticosteroids (ICS) Minor characteristics (at least 2 out of the following)

    1. Requirement for daily treatment with a controller medication in addition to ICS e.g. LABA, theophylline, leukotriene antagonist
    2. Asthma symptoms requiring SABA on a daily or near daily basis
    3. Persistent airways obstruction (FEV1 <80% predicted, diurnal PEF variation >20%)
    4. One or more emergency care visits for asthma per year
    5. 3 or more steroid "bursts" per year
    6. Prompt deterioration with ≤ 25% reduction in oral or ICS
    7. Near fatal asthma event in the past

Exclusion Criteria:

• Current smokers, or less than 3 years since quitting smoking (< 5 pack/years)
• Less than 4 weeks from an exacerbation
• On steroid-sparing agent or immunosuppressant such as azathioprine, methotrexate and ciclosporin
• Concomitant anti-IgE therapy
• On anti-platelet or anti-coagulant drugs
• Low platelet count
• Pregnancy or breast-feeding
• Intubation for asthma within 6 months of entry into this study (if undergoing bronchoscopy)